Identification documents (“ID documents”) play a critical role in today's society. One example of an ID document is an identification card (“ID card”). ID documents are used on a daily basis—to prove identity, to verify age, to access a secure area, to evidence driving privileges, to cash a check, and so on. Additionally, because we live in an ever-evolving cashless society, ID documents are used to make payments, access an automated teller machine (ATM), debit an account, or make a payment, etc.
For the purposes of this disclosure, ID documents are broadly defined, and include, e.g., credit cards, bank cards, phone cards, passports, driver's licenses, network access cards, employee badges, debit cards, security cards, visas, immigration documentation, national ID cards, citizenship cards, social security cards, security badges, certificates, identification cards or documents, voter registration cards, police ID cards, border crossing cards, legal instruments, security clearance badges and cards, gun permits, gift certificates or cards, membership cards or badges, etc.
Many types of ID documents carry information relating to the identity of the bearer. As this information varies from one document to another, the document design needs to enable a method for printing or otherwise recording variable data on the document. Examples of variable data include personalization information like the bearer's name, address, birth date, signature, photographic image and other biometric data (e.g., a fingerprint, a facial image or template, or iris or retinal template). ID documents often include both variable data as well as fixed data (e.g., data that remains fixed across a set of cards like the issuer name, jurisdiction, lot number, etc.). In some cases, the fixed data is pre-printed on an ID document during manufacturing, while variable data is printed at the time of enrollment when the prospective bearer provides personalization information.
ID documents typically include security features, as well as machine readable features such as bar codes, a magnetic stripe or other magnetic storage media, IC chip or other electronic storage media, RFID tag, digital watermark, optical memory device, etc.
Technology for capturing bearer information and printing ID documents has evolved considerably, and there are a variety of methods in use. The advent of commercial apparatus (printers) for producing dye images by thermal transfer has made relatively commonplace the production of color prints from electronic data acquired by a video camera. In general, this is accomplished by the acquisition of digital image information (electronic signals) representative of the red, green and blue content of an original, using color filters or other known means. Devices such as digital cameras, optical sensors, and scanners also can provide digital image information. The digital image information is utilized to print an image onto a data carrier. For example, information can be printed using a printer having a plurality of small heating elements (e.g., pins) for imagewise heating of each of a series of donor sheets (respectively, carrying diffuseable cyan, magenta and yellow dye). The donor sheets are brought into contact with an image-receiving element (which can, for example, be a substrate), which has a layer for receiving the dyes transferred imagewise from the donor sheets. Thermal dye transfer methods are described, for example, in U.S. Pat. No. 4,621,271, issued Nov. 4, 1986 to S. Brownstein and U.S. Pat. No. 5,024,989, issued Jun. 18, 1991 to Y. H. Chiang, et al. Each of these patents is hereby incorporated by reference.
Dye diffusion thermal transfer printing (“D2T2”) and thermal transfer (also referred to as mass transfer printing) are two printing techniques that have been used to print information on identification cards. For example, D2T2 has been used to print images and pictures, and thermal transfer has been used to print text, bar codes, and single color graphics.
D2T2 is a thermal imaging technology that allows for the production of photographic quality images. In D2T2 printing, one or more thermally transferable dyes (e.g., cyan; yellow, and magenta) are transferred from a donor, such as a donor dye sheet or a set of panels (or ribbons) that are coated with a dye (e.g., cyan, magenta, yellow, black, etc.) to a receiving layer (which could, for example, be part of an ID document) by the localized application of heat or pressure, via a stylus or thermal printhead at a discrete point. When the dyes are transferred to the receiver, the dyes diffuse into the receiving layer (or ID card substrate), where the dyes will chemically be bound to the substrate or, if provided, to a receptor coating. Typically, printing with successive color panels across the document creates an image in or on the document's surface. D2T2 can result in a very high printing quality, especially because the energy applied to the thermal printhead can vary to vary the dye density in the image pixels formed on the receiving layer, to produce a continuous tone image. D2T2 can have an increased cost as compared to other methods, however, because of the special dyes needed and the cost of D2T2 ribbons. Also, the quality of D2T2-printed image may depend at least on an ability of a mechanical printer system to accurately spatially register a printing sequence, e.g., yellow, magenta, cyan, and black. For more information about D2T2 printing for ID documents and related technology, see U.S. Pat. No. 6,066,594, which is hereby incorporated reference.
Another thermal imaging technology is thermal or mass transfer printing. With mass transfer printing, a material to be deposited on a receiving layer (such as carbon black (referred to by the symbol “K”)) is provided on a mass transfer donor medium. When localized heat is applied to the mass transfer donor medium, a portion (mass) of the material is physically transferred to the receiving layer, where it sits “on top of” the receiving layer. For example, mass transfer printing often is used to print text, bar codes, and monochrome images. Resin black mass transfer has been used to print grayscale pictures using a dithered gray scale, although the image can sometimes look coarser than an image produced using D2T2. However, mass transfer printing can sometimes be faster than D2T2, and faster printing can be desirable in some situations.
Printing of black (“K”) can be accomplished using either D2T2 or mass transfer. For example, black monochrome “K” mass transfer ribbons include Kr (which designates a thermal transfer ribbon) and Kd (which designates dye diffusion).
Both D2T2 and thermal ink have been combined in a single ribbon, which is the well-known YMCK (Yellow-Magenta-Cyan-Black) ribbon (the letter “K” is used to designate the color black in the printing industry). Another panel containing a protectant (“P”) or laminate (typically a clear panel) also can be added to the YMCK ribbon).
In addition to these forms of printing, other forms of printing and applying variable data are used in ID documents, including ink jet printing, laser printing and laser engraving.
In many ID document applications, there is a need to integrate document structure for printing variable information, such as the bearer's personal information, as well as a host of other security features and machine readable features. The need to support different features poses a number of challenges because these features often use different materials with different attributes and related manufacturing processes. For example, some features require special materials to enable printing, recording or reading of information. These materials also have different resistances to wear and tear and may require particular processes and materials to join them together (e.g., lamination and adhesive), as well as different layers to protect them or facilitate information recording and reading functions (e.g., protective coatings, image receiving layers, transparent layers for optical reading, etc.). When not formulated correctly, the various materials can interact and result in both reduction in the manufacturing yield of the ID documents and degradations of the printed information or properties of other conflicting features on the document while in circulation due to normal wear and tear.
One particular challenge is posed by ID documents that require both variable printing of personal information as well as areas for supporting reading and writing to optical memory. Optical memory devices require clear optical paths for writing and reading to the device in the document. One type of optical memory device is the optical storage media used in optical memory cards from LaserCard Systems Corp. of Mountain View, Calif. The manufacturer creates card stock by combining webs of polycarbonate film with silver based optical storage media using an acrylate based adhesive system, cured with an electron beam process. The optical storage media occupies areas of the card stock and requires a clear optical path over a substantial portion of this area. To protect the optical path, the manufacturer applies a clear protective hard coat (e.g., acrylic hard coat) over the card stock. The manufacturer then applies a D2T2 image receiving layer over the protective hard coat to enable variable printing of personalized information. This process includes laminating strips of vinyl as the receiving layer with associated adhesive onto the protective coating of the card stock. The application of the image receiving layer in this fashion is disadvantageous because it involves a slow and tedious lamination process, and the resulting structure of receiving layer on hard coat is subject to de-lamination during manufacture and use in the field.
The invention provides hard coat and image receiving layer structures and related methods used in ID document production. These structures and methods provide ID documents that offer hard protection in areas where needed (e.g., in optical windows for optical machine readable data), and also provide image receiving layers for later printing of variable data, such as personalization information of the bearer. Implementations of the structure provide an effective interface between hard coat and image receiving layers that provides enhanced durability in manufacture and field use.
One aspect of the invention is an identification document structure. The structure comprises an image receiving layer on a document that includes an optical storage device. The image receiving layer covers first area of the document surface. The structure includes a hard coat layer on the image receiving layer. The hard coat layer covers a second area of the document structure corresponding to an optical window of the optical storage device. The hard coat layer does not cover at least a portion of the first area to enable the image receiving layer to receive variable printing after application of the hard coat layer. In one particular implementation, the hard coat layer is applied in stripes on a D2T2 image receiving layer and cured to create a durable interface between the hard coat and image receiving layers.
Another aspect of the invention is an identification document film comprising a polymer layer and an image receiving layer on the polymer layer. The image receiving layer covers a first area of the polymer layer. The film also includes a hard coat layer on the image receiving layer. The hard coat layer covers a second area of the polymer layer corresponding to an optical window for an optical storage device. The hard coat layer does not cover at least a portion of the first area to enable the image receiving layer to receive variable printing after application of the hard coat layer.
Another aspect of the invention is an identification document film comprising a polymer layer, an image receiving layer, and a hard coat layer. The hard coat layer and the image receiving layer are interleaved over the polymer layer such that the hard coat layer provides an optical window for an optical storage device, and the image receiving layer is operable to receive variable printing. In one embodiment, the film includes a primer on the polymer layer. The hard coat and image receiving layer are interleaved and applied to the primer on the polymer layer. In an alternative embodiment, the image receiving layer and the hard coat layer are interleaved and applied directly to the polymer layer.
Yet another aspect of the invention is a method of making a film for an identification document. The method provides a polymer layer with a first surface area. It then applies an image receiving layer to at least a portion of the first surface area, and applies a hard coat layer to at least a portion of the image receiving layer. The hard coat layer provides protection for an optical window of an optical storage medium. The image receiving layer is operable to receive personalized printing after the hard coat layer is applied.
Further features will become apparent with reference to the following detailed description and accompanying drawings.